1. Field of the Invention
The present invention generally relates to an optical disk apparatus for recording and reproducing information to and from a optical disk capable of recording data such as a CD-R/RW, DVD−R/RW, DVD+RW, or a like.
2. Description of the Related Art
Conventionally, it is required to complete writing data to be recorded to the optical disk capable of recording data such as a CD-R/RW, DVD−R/RW, DVD+RW, or a like, at once. Such a conventional once writing operation is called “Track at Once” or “Disc at Once”. During the conventional once writing operation, in a case in which a writing speed is faster than a data transmission speed from a host computer and data to be written to the optical disk is interrupted, that is, in a case in which a buffer under-run occurs, it ends up failing to write data to the optical disk.
The faster a data write operation is conducted, the more the buffer under-run occurs. Especially for a medium that is not re-writable such as a CD-R, an occurrence of the buffer under-run is a fatal error. Conventionally, in a method for avoiding the buffer under-run, a capacity of a buffer RAM (Random Access Memory) (for example, a memory consisting of a DRAM (Dynamic Random Access Memory)) is increased or a speed of writing data to the optical disk is set to be slower than that of transmitting data from the host computer.
Japanese Laid-Open Patent Application No.10-49990 discloses that instead of avoiding the buffer under-run, the data write operation is temporarily interrupted when the buffer under-run occurs, the data write operation is resumed from an interrupted location on the optical disk after a sufficient amount of data is transferred from the host computer and accumulated in the buffer RAM. Accordingly, during the data write operation to the optical disk, even when the fatal buffer under-run that is a fatal error occurs, it is possible to complete writing data properly to the optical disk without a failure of writing data.
However, in a recording control as disclosed in the Japanese Laid-Open Patent Application No.10-49990, a data recording operation to the optical disk may be frequently stopped and resumed. Generally, data transferred from the host computer is temporarily maintained in the buffer RAM and a predetermined parity code is encoded and additionally provided in the data. After that, a CIRC process, an EFM (Eight to Fourteen bit Modulation) encoding process, or a like is conducted for the data and the data is recorded as record data on the optical disk. Recently, in a general optical apparatus, a capacity of the buffer RAM is approximately 512 Kbytes to 8 Mbytes.
For example, a recording speed of a CD is 150 Kbytes/sec at standard speed. In correspondence to a recent improvement of the recording speed, the recording speed of the CD becomes 2.4 Mbytes/sec at 16-times speed record. Thus, a recording time for recording the data temporarily maintained in the buffer RAM is relatively limited. That is, it is required to transfer new data during the recording time. Otherwise, the buffer under-run occurs and the recording operation is temporarily stopped. Even though performance of host computer connected to the optical disk apparatus is improved, in order to secure a stable operation for any host computer, it is required for the optical disk to conduct an operation for a case in which the recording operation is temporarily stopped and resumed frequently.
However, under a circumstance in which the recording operation is frequently stopped and resumed, when an end location previously recorded is detected and it is controlled to resume recording precisely from the end location, a displacement amount between absolute location information and a location where data is recorded on the optical disk is accumulated. In this case, when the displacement amount exceeds a constant value, the recording operation cannot be resumed. That is, as described above, a data amount capable of maintaining data transferred from the host computer at once is limited to a maximum capacity of the buffer RAM. Thus, it is required to temporarily stop the recording operation if data is not transferred from the host computer again before the optical disk apparatus completes recording data accumulated in the buffer RAM. The smaller the capacity of the buffer RAM, or the faster the recording speed for recording data to the optical disk, the more frequently the buffer under-run occurs.